The ability to deliver enhanced subscriber services from an Advanced Intelligent Network (AIN) on land-line telecommunication systems is well established. These services typically involve executing service logic on an external platform, which may include, for example, accessing a database that resides on another network element external to the local switch and retrieving call processing information. Examples of such services include 800 Services, Credit Card Verification, Geographic Call Routing, Flexible Call Routing, Flexible Carrier Selection, CLASS Services, and Single Number Service.
One system for delivering enhanced subscriber services using an AIN is described in U.S. Pat. No. 5,377,186 to Wegner, et al. The system uses a Local Switch (LS) connected through an AIN to a Service Control Point (SCP) wherein a subscriber services database resides. The LS is provisioned for Integrated Services Digital Network User Part (ISUP) call-setup protocol. A number of loop-back trunks with defined Circuit Identification Code (CIC) pairs are also provisioned on the LS. In addition, the routing table in the LS is modified to route the ISUP messages for calls requesting the enhanced subscriber service to the SCP, and to route the voice signal to the outbound connection of one of the loop-back trunks. The SCP is modified so that an ISUP interface will perform AIN-type services, e.g., number translation, using parameters in the ISUP call-setup protocol that were originally intended for conditions such as call forwarding. When a call requesting the enhanced user service is received by the LS, an ISUP Initial Address Message (IAM) is routed to the SCP and voice is directed to the CIC of the outbound connection of a loop-back trunk. When the SCP receives the IAM message, the ISUP interface treats the IAM message as a Query message requesting retrieval of a subscriber service. The SCP responds to the query and returns a new routing number, or translated destination, for the call. The ISUP interface generates an IAM (Call-Forward) message that includes the new routing number and the CIC of the inbound connection of the loop-back trunk. The IAM (Call-Forward) message is then sent back to the originating MSC directing the MSC to initiate a new call to the translated destination, thus connecting the original call to the translated destination via the loop-back trunk.
The invention described in the patent to Wegner, et al., may generally be applied to cellular radio telecommunication systems by incorporating the suggested changes to the LS into a Mobile Switching Center (MSC) of a cellular system that includes an AIN.
One problem with the ISUP approach described above, as generally applied to a cellular systems, is that many MSCs in North America do not support ISUP call set-up protocol, and as such can't use this method. Another problem is that the ISUP approach requires hard-wiring one or more loop-back trunks in the MSC, and associating these trunks with a single SCP through routing table entries. This requires permanently tying up valuable resources in the form of loop-back trunks. This also requires that periodic traffic studies be completed in order to balance the expense of dedicating the loop-back trunks to an SCP against an acceptable grade of service. Another problem is that the ISUP method is directed only to enhanced subscriber services of the destination translation type and does not allow enhanced services that require suspension of call processing.
Accordingly, it is an object of the present invention to describe a system that can utilize the IS-41 messaging protocol, which is the protocol that is typically provisioned on all MSCs.
Another object of the invention is to describe a system that uses resources only as needed.
Another object of the invention is to describe a system that is flexible enough to be applied to any enhanced service, including those where an SCP interacts with a user call in a triggered environment that may include suspension of call processing.